1. Field of the Invention
The present invention relates to a motion picture camera.
2. Description of the Prior Art
Recently in the field of the small motion picture cameras in which an 8 m/m film is used, a film cartridge in which a film is contained and which can be used together with the film contained therein is usually adopted in order to facilitate loading and unloading the film into and out of the camera respectively. To load the film into the camera, the film cartridge is loaded into the cartridge chamber of the camera, and to take the film out of the camera, the film cartridge is taken out of the cartridge chamber. This kind of conventional cartridge is capable of recording only the picture information on the film, being incapable of recording the sound information on the film. However a large number of people now desire that the picture information be recorded simultaneously with the sound information. To accomplish such simultaneous recording another sound recording device which is independent of the motion picture camera for recording the picture information on the film and which can be selectively mounted and dismounted on the motion picture camera is connected to the motion picture camera in such a manner that the picture information and the sound information are recorded simultaneously. Thus the picture information is recorded on the film by means of the motion picture camera while the sound information is recorded on the second recording tape by means of the sound recording device.
However, in case the picture information and the sound information are recorded simultaneously in accordance with the conventional simultaneous sound recording system, both the motion picture camera and the sound recording device must be prepared and separately set up. This reduces the mobility peculiar to the small motion picture camera using 8 m/m film. To always be required to separately bring or carry both the motion picture camera and the sound recording device causes a number of problems to control and handle plural pieces of equipment.
Quite recently however, in order to solve the above mentioned problems a film cartridge containing a film having a sound recording portion so as to be capable of recording the sound information and also being capable of recording the picture information on the same film has appeared in the industry. A motion picture camera capable of recording the sound information and the picture information on the same film simultaneously, namely the so called simultaneous sound recording motion picture camera has also been recently developed.
Examples of the simultaneous film cartridge and the motion picture camera of this kind have been disclosed in U.S. Pat. Nos. 3,782,812; 3,825,327; 3767,294; 3,785,726.
In the film cartridge capable of simultaneous sound recording, as is disclosed in detail in U.S. Pat. No. 3,782,812, apart from the conventional picture recording opening another opening for sound recording is provided, whereby the film is fed to the sound recording opening at a constant speed when the film cartridge is loaded, while by means of the sound recording means, such as a magnetic head the sound information is recorded on the sound recording portion, which can be a magnetic coating provided on the film.
Further the motion picture camera in which a simultaneous sound recording film cartridge is used, can also use the conventional film cartridge which is only capable of recording the picture information.
With the appearance of the simultaneous sound recording film cartridge and the simultaneous sound recording motion picture camera it has become easy to record the sound information and the picture information on the same film simultaneously as well as being able to house the system in a very compact structure in comparison with the conventional system.
However, this simultaneous sound recording motion picture camera includes the sound recording device for recording the sound information in addition to the mechanism of the conventional motion picture camera for only recording the picture information, so that the shape and weight of such a camera has become large in comparison with the conventional motion picture camera so. The ease of mobility, which is one of the features of the small motion picture cameras in which an 8 m/m film is used is somewhat last. The mechanical part of this sound recording device principaly consists of the magnetic head, the head pad, the film guide member, the capstan, the pinch roller, the capstan, driving member, the fly wheel and so on. Of all these elements, the fly wheel is problematic because of its weight and shape.
This sound recording device is so designed that by means of the capstan and the pinch roller the film is fed in such a manner that the film runs across the magnetic head at a constant speed. The film is led to the magnetic head, being guided by means of the film guide part for controlling the running course of the film in such a manner that the sound information recording portion on the film runs by a certain determined position of the magnetic head member, while by means of the magnetic head member the sound information is recorded magnetically on the sound information recording portion on the film.
In this case, the film is fed by means of the capstan and the pinch roller provided behind the magnetic head member, whereby it is essential that the film runs by the magnetic head member always at a constant speed. Thus the rotation speed of the capstan shaft for feeding the film must be constant, namely of an equal angular speed. Therefore the capstan shaft is normally provided with a fly wheel so as to absorb small fluctuations of transmitted energy, minimizing the speed fluctuation during one rotation.
The effect of this fly wheel is represented by the moment of inertia. The larger the moment of inertia, the more speed fluctuation. Energy fluctuation is absorbed during one rotation in such a manner that the rotation is kept as nearly constant as possible. In order to increase the moment of inertia of this fly wheel, it is essential to increase the diameter and the weight of the fly wheel itself. However, this also increases the shape and the weight of the camera itself. This makes the small motion picture camera, in which an 8 m/m is used, lose its mobility which is one of the features of such a motion picture camera. This is an inevitable problem when the fly wheel is used in order to avoid the speed fluctuation.
Further as a problem peculiar to the simultaneous sound recording motion picture camera, the film has to be fed across the magnetic head member at a constant speed while the film is fed intermittently by means of the film feeding claw across the exposure opening for recording the picture information. As a result, it is possible that the film feeding at a constant speed could be influenced by the speed fluctuation due to the vibration arising from the intermittent feeding of the film. Further it is possible that the film feeding at a constant speed could be influenced by the elongation of the belt for transmitting the power from the driving motor to the capstan and by the precision of the capstan and of the rotary part for rotatably supporting the capstan.
In view of the foregoing, if it is possible to find a method to rotate the capstan shaft at an equal angular speed instead of the method of rotating the capstan shaft by means of the belt through the fly wheel, and also to find a method of eliminating the undesired influence of the intermittent movement of the film upon the sound recording, the characteristics of the motion picture can be utilized to its best advantage without losing the efficiency of the simultaneous sound recording motion picture camera.